1. Field of the Invention
The present invention relates to testing equipment, and more specifically to an acoustically quiet passive load device for use as a dynamometer for testing of low speed high output motors. Low speed high output motors are commonly used on ships and are required to operate without excessive acoustic noise and vibration. Such motors require testing by equipment that is designed to convert the power from the test motor into either potential energy or into energy absorbed by a device similar to that being tested. When potential energy is provided as the output large space requirements are an inherent disadvantage, as is the necessity for providing physical shielding mechanical barriers or the like to satisfy safety requirements. Where the power absorbing device is itself similar to the low speed high output motor being tested detection and measurement of the noise and vibration of the motor being tested can be very difficult to achieve.
2. Description of the Prior Art
Dynamometers with rotary discs or drums are well known. In particular, Bonomo U.S. Pat. No. 4,062,233 discloses a rotating drum dynamometer wherein the drum is mounted for rotation within a fluid filled container. Hydraulic brakes are provided around the exterior of the drum. Although this prior art patent does disclose a rotary type dynamometer, there is no suggestion of isolating the dynamometer structure so as to avoid vibration and noise from the load absorbing dynamometer itself as is required in a test setup for low speed high output motors of the invention disclosed herein.
Cline U.S. Pat. No. 2,597,450 discloses a cooling system for a disc type dynamometer, but here again there is no suggestion in Cline of isolating the dynamometer so as to prevent vibration feedback and acoustic noise in connection with the testing of low speed high output motors.
McClure U.S. Pat. No. 3,757,909 shows a dynamometer in the form of a water brake wherein a rotatable housing is provided with stator discs so that the discs can be either counterrotated or free to rotate in either direction in the process of absorbing torque. Here again there is no suggestion in McClure of a dynamometer equipped with both acoustic and vibration isolating capability so as to permit the testing of low speed high output motors, such as those hydraulically driven motors used on naval ships in an environment that requires operation without creating excessive vibration and acoustic noise.